Dopamine Dynamics Promote Cooperative Behavior Not Just the Rewards Accompanying Cooperation

Research Hypothesis 1.Nucleus accumbens medial shell (NAcMedSh) dopamine (DA) specifically encodes 1s-synchronized successful cooperative actions, not social contact, motor execution, reward expectation or sensory cues. 2.Learned cooperation-related DA representations have asymmetric stability: they persist after switching to individual tasks, while naive animals need de novo learning for cooperation tasks. 3.NAc D1 receptor (D1R)-mediated phasic DA is necessary for cooperative behavior, with task-specific effects: low-dose D1R blockade selectively impairs cooperation without affecting basal locomotion or individual reward-seeking. Data Acquisition Data from 2-month-old male C57BL/6J mice, approved by UESTC Animal Ethics Committee. Behavioral paradigm: 1s time-window cooperative nose-poke task; paired mice get shared water reward only if nose-pokes fall within 1s, with full control paradigms. Neural recording: AAV2-hSyn-GRABDA3m injected into NAcMedSh; fiber photometry recorded DA dynamics, 405nm reference for artifact correction. Pharmacology: Bilateral NAcMedSh cannulas for microinjection of D1R antagonist SCH23390 or saline. Behavioral data: EthoVision XT 15 recorded core behavioral metrics. Dataset Structure 6 experimental folders with raw/preprocessed fiber data and behavioral markers; 4 Prism project files for statistical analysis, inter-group comparison and dose-response analysis. Key Findings & Interpretation 1.NAc DA specifically encodes cooperative actions, not external rewards: DA AUC for successful cooperation rose significantly with training (p=0.0001), failed triggers evoked no response; reward-related DA remained stable. Reward extinction eliminated reward DA, but cooperation DA stayed stable.Interpretation: Revises classic RPE theory; NAc DA assigns intrinsic motivational value to cooperation itself. 2.Asymmetric stability of cooperation DA: Cooperation-to-independent group had stable trigger DA post-switch; independent-to-cooperation group showed full de novo DA learning.Interpretation: Learned cooperation DA is consolidated like skill memory, with behavioral inertia. 3.D1R is necessary for cooperation with task specificity: Low-dose SCH23390 reduced cooperation success by 65.9% reversibly, no effect on locomotion/individual reward-seeking.Interpretation: Cooperation has higher dependence on D1R-mediated phasic DA, providing a preclinical target for social cooperation deficits. Data Use Guidelines Interpretation rules: Core metrics: cooperation success rate, inter-nose-poke interval, event-related ΔF/F0 Z-score/AUC. Significance: *p<0.05, **p<0.01, ***p<0.001, ****p<0.0001, ns=no significant difference. Reuse: Raw data reanalyzable via MATLAB/Python; Prism files replicate all statistics. Limitations: Data from male C57BL/6J mice; cooperation defined as 1s synchronized nose-pokes, not generalizable to other scenarios.